This invention relates to filters for use in hot cells. In particular, it is an improved structure for supporting a HEPA (high-efficiency particulate air) filter for use in nuclear hot cells.
Hot cells are areas in which work is performed on equipment or substances that produce significant levels of radiation that may be threatening to humans. As a result, the work that is done is performed by electromechanical manipulators, master-slave manipulators, and overhead cranes, operated from remote locations by humans who are shielded from the radiation. Air in hot cells is circulated to prevent the buildup of radioactive materials. It is also necessary to be concerned about gases emanating from process equipment in hot cells. This is referred to as Vessel Off Gas (VOG). Such air or other gas is generally filtered to remove from the air or VOG particulate matter that may be radioactive. The filters and their housings are thus located in the hot cell, and are radioactive or contaminated with radioactive materials. As a result, it is necessary to be able to change filter cartridges in such filters with electromechanical manipulators. Filters that are presently used for filtering air that is supplied to hot cells receive filter cartridges on horizontal rails. Cranes place the filter cartridges containing filter elements on the rails and electromechanical manipulators slide the cartridges horizontally into place. The filter cartridges are then elevated by screws into engagement with knife edges that seal the filter cartridges against the escape of radioactive material into the air stream. The screws are operated by power wrenches that are controlled by electromechanical manipulators. The process of changing filter cartridges thus requires a substantial number of operations by electromechanical manipulators.
Electromechanical manipulators that are used in hot cells are expensive to purchase and difficult to maintain. The amount of maintenance that they need is roughly proportional to the amount of use that they get. In general, reliability is increased as the amount of use of electromechanical manipulators is reduced.